NEO is a non-profit, community-based blockchain project. It is a distributed network that uses blockchain technology and digital identity for asset digitization, intelligent management of digital assets using intelligent contracts, and realization of “smart economy”. At present, Neo’s market capitalization ranks fifteenth in the world in coinmarket, and it is one of the blockchain projects that have attracted much attention. We found a denial of service vulnerability in the neo smart contract platform that an attacker could use to instantly crash the entire neo network.